The above-mentioned recording/reproducing system employs a digital highly-efficient encoding technology typified by MPEG2 (Moving Picture Experts Group Phase 2). With the digital highly-efficient encoding technology, the conventional recording/reproducing system has been capable of recording received transport streams for a long period of time without degradation in image quality. In most cases, however, each payload in a transport stream has been scrambled in view of video copyright protection.
Also, of the respective pictures encoded in accordance with MPEG2, the recording/reproducing system may perform a process of selectively reproducing pictures coded with an intra-frame coding scheme (such pictures are hereinafter referred to as I pictures, and such a process is hereinafter referred to as high-speed replay).
With reference to FIG. 9, a recording/reproducing system for performing high-speed replay is described below. In FIG. 9, the recording/reproducing system includes a data managing section 1001, a recording medium 1002, a selector 1003, a descrambler 1004, an MPEG system decoder 1005, and a position information generating section 1006.
The above-structured recording/reproducing system has three basic operation modes described below.
First, in a first operation mode, an externally-supplied transport stream TS that has arrived at the recording/reproducing system is branched into two. One transport stream TS is output to the data managing section 1001, while the other is output to the selector 1003.
The data managing section 1001 temporarily stores the input transport stream TS in an internal buffer, and then waits for position information PI to come from the position information generating section 1006.
In the first operation mode, the selector 1003 selects an input system of the externally-supplied transport stream TS, and then outputs the input transport stream TS as it is to the descrambler 1004.
The descrambler 1004 uses a descramble key to descramble the scrambled input transport stream TS. Thus, a transport stream DETS is reconstructed, which has now become a data string that can be parsed. The transport stream DETS is output to the MPEG system decoder 1005 and the position information generating section 1006.
The MPEG system decoder 1005 performs a decoding process on the input transport stream DETS to reproduce a video signal VS and an audio signal AS. Both the video signal VS and the audio signal AS are baseband digital signals. The video signal VS represents video for a program or the like, while the audio signal AS represents audio for a program or the like. The video signal VS is output to a display device (not shown), while the audio signal AS is output to an audio output device (not shown).
The position information generating section 1006 searches the transport stream DETS output from the descrambler 1004 for a transport packet whose payload includes a part of I pictures (hereinafter referred to as I-picture transport packet). When such an I-picture transport packet is found, the position information generating section 1006 specifies a bit location in the transport stream DETS of the relevant packet. Each bit location is output as position information PI to the data managing section 1001.
The data managing section 1001 responds to the input of the position information PI to start a process of generating an address table AT. As described above, the data managing section 1001 holds the transport stream TS in its internal buffer. However, the transport stream TS in the buffer has been scrambled. Therefore, the data managing section 1001 cannot directly find an I-picture transport packet from the transport stream TS. For this reason, the data managing section 1001 refers to the input position information PI to specify the bit location of the I-picture transport packet on the transport stream held in the buffer.
Furthermore, the data managing section 1001 determines which address area of a first storage area 10021 of the storage medium 1002 is used to record each transport packet of the transport stream TS held in the buffer, that is, assigns each transport packet an address area. Then, the data managing section 1001 collects only the address areas assigned to the I-picture transport packets to generate an address table AT.
Then, the data managing section 1001 writes each transport packet held in the buffer in the first storage area 10021. Also, the data managing section 1001 writes the generated address table AT in a second storage area 10022 of the storage medium 1002.
Next, a second operation mode, that is, normal replay, is described. In the second operation mode, the data managing section 1001 reads the transport stream TS sequentially from its head from the first storage area 10021, without consideration of the address table AT in the second storage area 10022, for output to the selector 1003.
The selector 1003 selects an input system on the data managing section 1001 side in the second operation mode, and then outputs the input transport stream TS as it is to the descrambler 1004.
The descrambler 1004 and the MPEG system decoder 1005 perform processing similar to that in the first mode to reproduce the video signal VS and the audio signal AS.
Next, a third operation mode, that is, high-speed replay, is described. In the third operation mode, the data managing section 1001 reads the address table AT from the second storage area 10022. The data managing section 1001 reads only I-picture transport packets from the address areas described in the read address table AT, and then outputs a transport stream TS′ composed of the read transport packets to the selector 1003.
For audio, in a case of double-speed replay, for example, the data managing section 1001 repeats a process of reading a transport packet of audio for one second, and then reading not a transport packet for the next one second but a transport packet representing audio after one second.
The selector 1003, the descrambler 1004, and the MPEG system decoder 1005 perform processing similar to that in the first operation mode to reproduce a video signal VS′ and an audio signal AS′.
The video signal VS′ is similar to the video signal VS in that both are baseband digital video signals, but is different therefrom in that reproduction is made only from I-picture transport packets. The audio signal AS′ is similar to the audio signal AS in that both are baseband digital audio signals, but is different therefrom in that reproduction is made only from transport packets representing a part of audio. Therefore, when the display device, typified by a television, processes the video signal VS′ and the audio signal AS′, a program is played at a speed higher than that in normal replay.
As described above, the conventional recording/reproducing system has a decode processing system configured by the selector 1003, the descrambler 1004, the MPEG system decoder 1005, etc., and a read/write processing system configured by the data managing section 1001, the storage medium 1002, etc., both systems being adjacently placed within a box.
In recent years, a plurality of display devices are often placed in a living space. Therefore, desires have risen for one read/write processing system to be placed at a specific location within a living space, while the decode processing system be placed closely to each of the plurality of display devices.
However, there has been a problem that high-speed replay is difficult to achieve by merely dividing the conventional recording/reproducing system into a read/write processing system and a decode processing system, and placing the read/write processing system and the decode processing system away from each other as being connected by a cable.
The reasons of the above are as follows. When the read/write processing system and the decode processing system are close to each other within the same box, the buffer provided in the data managing section 1001 can absorb a difference between a time when the transport stream TS arrives at the data managing section 1001 and a time when the position information PI arrives there. However, when the read/write processing system and the decode processing system are placed away from each other, it is not possible to accurately know approximately how long the position information PI will delay for arrival time of the transport stream TS. Such a deviation in arrival timing may prevent the managing section 1001 from generating the address table AT. Consequently, high-speed replay is difficult to achieve.
Also, in the conventional recording/producing system, the transport stream TS and the address table AT are written in different storage areas in the storage medium 1002. Therefore, there has been another problem that a writing process performed by the data managing section 1001 is complex.
Therefore, an object of the present invention is to provide a recording/reproducing system capable of easily performing high-speed replay.
Another object of the present invention is to provide a recording/reproducing system capable of performing high-speed replay even when the decode processing system and the read/write processing system are placed away from each other.